1. Technical Field
The present invention relates to a pointing device and a touch detection system.
2. Description of the Related Art
Display apparatuses with a touch detection function have recently been attracting attention. Such display apparatuses are obtained by mounting a contact detecting device called a touch panel on a display device, such as a liquid-crystal display device, or integrating the touch panel with the display device. The display apparatuses display various button images and other images on the display device instead of typical mechanical buttons to receive information. Because the display apparatuses with a touch panel require no input device, such as a keyboard, a mouse, or a keypad, they are increasingly used for computers, portable electronic apparatuses, such as mobile phones, and other equipment.
Some types of touch detection technologies are known, including capacitive touch panels that require low power consumption. Display apparatuses with a touch detection function including such a capacitive touch panel, for example, may have the following configuration: common electrodes for display originally included in the display apparatuses are also used as one of a pair of touch sensor electrodes, and the other of the electrodes (touch detection electrode) is arranged in a manner intersecting with the common electrodes. The display apparatuses with a touch detection function sequentially apply a drive signal to the common electrodes to perform linear sequential scanning, thereby performing a display operation. In addition, the display apparatuses with a touch detection function analyze a touch detection signal generated in the touch detection electrode in response to the drive signal based on the fact that capacitance formed between the pair of touch sensor electrodes changes depending on an external proximity object, thereby performing a touch detection operation.
In touch detection systems with such a touch panel, a user may perform a touch operation using the finger or a pointing device, such as a stylus pen (an active pen or an electronic pen). Japanese Patent Application Laid-open Publication No. 2014-206933 (JP-A-2014-206933) discloses a touch panel controller capable of determining that a touch is made by the hand of a user when the perimeter of a region in which the touch is detected is equal to or larger than a threshold.
When the user performs a touch operation with the pointing device held in the hand, the following case may possibly occur: if the hand of the user holding the pointing device comes into contact with the touch panel, the touch is detected at a position unintended by the user, that is, a position where the hand of the user comes into contact with the touch panel. To address this, JP-A-2014-206933 also describes what is called a palm rejection function to exclude a touch operation when it is determined to be a touch operation performed by the hand of the user.
When the conventional technology described above determines an operation to be a touch operation performed by the hand of the user, however, the region in which a touch is detected is not necessarily made by the hand holding the pointing device. To transmit the fact that the user is performing the touch operation with the pointing device held in the hand, a wireless communication function, such as Bluetooth (registered trademark) may be used. In this case, the pointing device needs to have a wireless communication function other than the touch operation.
For the foregoing reasons, there is a need for a pointing device and a touch detection system that can exclude a touch operation performed by a hand holding a pointing device simply by the touch operation.